This application claims the priority of German application 101 54 484.7, filed Nov. 8, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention concerns both an apparatus and a method for indirectly determining a temperature at a predetermined location in an internal combustion engine.
The demands on modern engine management have increased with respect to consumption, performance, emissions, and because of competition. So-called engine heat management is a component that leads to improvement or optimization of all of these disciplines, especially in diesel engines. One of its objectives is to heat the engine to a desired nominal temperature as rapidly as possible. Furthermore, a maximum allowed operating temperature should not be exceeded in the continuous operation.
For this purpose, knowing the temperature at a special position in the cylinder head is of great importance. The temperature at a bridge between two exhaust valves of the internal combustion engine is of particular interest. For construction reasons, suitable direct detection of this temperature for series production is not possible via sensor technology.
German patent publication DE 40 14 966 A1 describes an engine diagnostics method wherein the combustion chamber temperature is determined indirectly. A glow plug configured as a sensor element is used for this purpose. The temperature-dependent internal impedance of the glow plug or the filament is evaluated and the temperature of the internal combustion engine is determined based thereon.
It is an object of the invention to determine in a simple manner a temperature at a location that is difficult to access in an internal combustion engine with the least additional construction complexity.
This object is attained by way of an apparatus for indirectly determining a temperature at a predetermined location in an internal combustion engine which has a sensor that can measure a component temperature mounted on the internal combustion engine, other sensors provided to directly or indirectly detect rpm, a quantity of injected fuel, a temperature of charge air, and coolant temperature as other input variables, and a control unit which can determine the temperature at the predetermined location from the component temperature and the other input variables. The object is also attained by way of method for indirectly determining a temperature at a predetermined location in an internal combustion engine including measuring a component temperature in the internal combustion engine, directly or indirectly determining an engine rpm, a quantity of injected fuel, a temperature of charge air, and a coolant temperature, and calculating the temperature at a predetermined location in a control unit from a component temperature, the engine rpm, the quantity of injected fuel, the temperature of the charge air, and the coolant temperature.
With an apparatus in accordance with the invention, it is possible to determine in a simple manner the temperatures in areas of an internal combustion engine that are difficult to access. For this purpose, a sensor for determining a component temperature is mounted in an area that is easier to access. In addition, based on the component temperature determined in this manner and other input variables, the temperature is then determined at locations that are difficult to access. Additional input variables are considered, such as the engine rpm, the quantity of injected fuel, the temperature of the charge air, and the coolant temperature. These are either determined directly via sensors, or are already available in the control unit of the internal combustion engine as calculated variables. The temperature at the difficult-to-access areas of the internal combustion engine can be determined via this apparatus without utilizing major construction measures.
The sensor for determining the component temperature is preferably mounted in a position that is accessible from outside. This has the advantage of easier electrical contact and the possibility of exchanging the sensor.
The apparatus for determining the temperature is preferably used on a bridge between two exhaust valves of the internal combustion engine. This temperature is of great importance, since this component is highly loaded thermally, on the one hand, and the material thickness at this location is relatively small, on the other hand. The temperature determined in this way can also be used as an input variable for engine control.
A formula for indirect calculation has proven to be useful in tests. The input variables that were used therein, the engine rpm, the quantity of injected fuel, the temperature of the charge air, and the coolant temperature, were determined to be not only necessary but also sufficient for the specification of the physical processes. Improved accuracy in the determination can be achieved by using other input variables.
Other advantages and practical embodiments can be drawn from the other claims, the description of the figures, and from the drawings.